Oh, If you don't know what those terms mean, it's no wonder you're confused.
Some people like to install custom ROMs on their phone. A ROM is like an operating system. Like if you wanted to use something other than Microsoft Windows, (Apple Mac OS, or some type of Linux, etc.) on your computer. To install a different ROM from the ROM that came with your phone, you need to "Root", install a "Custom Recovery", then "Flash the ROM". There are instructions for all of this in the "Rooting, Hacks and ROMs" subforum here on androidcentral, but honestly, if you don't want to screw with it, don't.
You have a phone you've never messed with, and it's not working right. Take it back in and demand they fix it.